In adults, when the heart rhythm controlled by the sinus node exceeds 100 beats per minute, it is called sinus tachycardia. It is the most common type of tachycardia and is often associated with sympathetic excitation and decreased vagal tone. It is not a primary arrhythmia and can be caused by a variety of factors. It can be caused by exercise, panic, anxiety, and emotional stress in physiological states, or it can occur after the application of drugs such as epinephrine and isoprenaline. It is highly likely to occur in the presence of fever, hypovolemia, anemia, hyperthyroidism, respiratory insufficiency, hypoxemia, hypokalemia, heart failure, and other cardiac disorders. After correcting the primary disease or controlling the triggering factors, the rapid heart rate can be reduced to normal level. 1.Physiological factors There are many factors that affect heart rate, such as physical activity, emotional excitement, full meals, strong tea and coffee, smoking, alcohol, etc. can make the sympathetic nerve excited and heart rate accelerated. The sympathetic nerves are excited and the heart rate is accelerated when the body position is changed, while the heart rate is slowed down when the body position is lying down. Sinus tachycardia caused by physiological factors is often transient, after the above factors are removed, the heart rate will soon return to normal, and the duration is short. 2, pathological factors (1) heart failure, especially in the early stages of heart failure, the heart rate is often increased. (2) Hyperthyroidism Most hyperthyroid patients have sinus tachycardia, with heart rate generally ranging from 100 to 120 beats per minute, and in severe cases the heart rate can reach 120 to 140 beats per minute. (3) In acute myocardial infarction, the incidence of sinus tachycardia can reach 30% to 40% during the course of acute myocardial infarction. (4) Shock can cause sinus tachycardia, and the heart rate can reach more than 100 beats per minute in mild shock; in severe shock, the heart rate is faster and can be greater than 120 beats per minute. (5) Most patients with acute myocarditis may develop sinus tachycardia that is disproportionate to the increase in body temperature. (6) Other anemia, fever, infection, hypoxia, pain, autonomic dysfunction, malnutrition, and post-operative cardiac surgery can all result in sinus tachycardia. (7) Drugs such as epinephrine and atropine can also cause sinus tachycardia.